1. Field of the Invention
This invention relates broadly to cardiothoracic imaging. More particularly, this invention relates to segmenting cardiac chambers in a four-dimensional magnetic resonance image.
2. State of the Art
Accurate and reproducible assessment of the left and right ventricular volumes and ejection fraction is essential for the prognosis of patients with heart disease and for evaluating therapeutic response. Magnetic resonance (MR) imaging has proven to be an accurate and reproducible imaging technique for the quantitative analysis of left and right ventricular functions. Ventricular volumes and mass as well as regional functional parameters such as wall motion and wall thickening, especially for the left ventricle, can be obtained in the true short-axis plane of the ventricle. These short-axis views have various advantages. Since wall motion and wall thickening takes place mainly perpendicularly to the viewing direction, they can be followed best in this direction. Furthermore, partial volume effects are minimized. A major advantage of MR imaging is that it does not use ionizing radiation and is non-invasive since no contrast agent is used. Through using multiple imaged slices a combination of spatial and time coordinates is considered.
Chris A. Cocosco, in “Automatic cardiac region-of-interest computation in cine 3D structural MRI”, CARS and Elsevier, 2004, describes a method for extracting a region of interest around the heart in short-axis MRI cardiac scans. The method produces a region within four-dimensional (4D) datasets wherein the left and right ventricles are localized. No attempt is made to differentiate between the left and the right ventricle. Neither are the base and apex locations of the ventricle(s) defined. The method may in particular fail whenever high local variances are present in the 4D dataset that may originate from main blood vessels (lung/aorta) or from specifically superimposed text such as trigger time. The method may also fail when the 4D image contains an inhomogeneity. This inhomogeneity can be caused by lower sensitivity at a larger distance between the heart and the imaging coils of the MR apparatus which then leads to lower pixel intensity in the image.